[PATCH 0/4] Change how stdlog timestamps are written

[Tom Tromey <tom@tromey.com>]

I've been looking at the GDB ui_file and pager system to see if it can
be made more understandable -- right now it's fairly spaghetti-ish,
with ui_file calling into functions in util.c, that then dispatch back
to ui_file.  My vision for the endpoint is something along the lines
of Java's stream writers, where additional functionality is provided
by just instantiating some new writer to wrap an existing one.

This series is a step toward that long-term goal.  It changes how
gdb_stdlog timestamps are written, moving this into a new ui_file
subclass.  This avoids a special case (which may in some situations be
incorrect, see patch #4) in vfprintf_unfiltered.

Regression tested on x86-64 Fedora 34.

Let me know what you think.

Tom